1. Field of the Invention
The present invention relates to a pressure sensitive sensor for detecting an external force by a housing elastically deformed by external pressure and electrodes provided in the housing contacting each other, and to a pressure sensitive sensor terminal processing method and manufacturing method.
2. Description of the Related Art
There are pressure sensitive sensors in which a plurality of electrodes made of metal plates, metal wires or the like are disposed within an elastically deformable housing so as to be spaced apart from one another. The housing is elastically deformed by pressure such that the plurality of electrodes contact one other, thereby causing electrical continuity, or a short-circuit, so that the pressure is detected.
In such a pressure sensitive sensor, terminal portions are open in order to be coupled to a connecting means, such as a cord, extending from a determination means such as a computer. Therefore, usually, the connecting means and the electrodes are coupled and then sealed to prevent malfunctioning resulting from, for example, entry of water. From the viewpoints of the reliability of the seal and work efficiency in the sealing operation, it is preferable that the seal used is formed by, for example, molding the terminal portions of the pressure sensitive sensor including the vicinity of the terminals of the connecting means with a synthetic resin material from the outside, in a state in which the terminals of the electrodes are connected to the connecting means.
However, when molding is carried out by using a synthetic resin material, while the connecting means and the electrodes are coupled, the terminal portions of the pressure sensitive sensor are put into the interior of a mold or the like. In this state, molten synthetic resin material is injected to effect molding as in the case of injection molding. Therefore, there is the possibility that the pressure applied during injection of the synthetic resin material will cause the electrodes exposed from the end portion of the housing to contact each other and make electrical continuity.
In addition, there is the possibility that during molding, the molten synthetic resin material will enter the spaces between the electrodes and such that dead zones are formed in places in the pressure sensitive sensor.
Due to these possibilities, it has been difficult to actually carry out terminal processing by molding.
In consideration of the above facts, a first object of the present invention is to obtain a pressure sensitive sensor and a pressure sensitive sensor terminal processing method capable of ensuring reliability of a seal, improving work efficiency of the sealing operation and enhancing reliability of the sensor itself.
To attain the first object stated above, the pressure sensitive sensor in a first aspect according to the present invention comprises: an insulating housing having a hollow interior and open terminal portions, said housing being elastically deformable by an external force; a plurality of electrode held within said housing in a state in which at least one end of each of said electrodes is pulled out and the respective electrodes are set apart from one another with a space therebetween, said electrodes being deformed by an external force acting on said housing so as to contact one another to make electrical continuity; an insulating spacer provided to come in contact with said plurality of electrodes correspondingly to the inner terminal portions of said housing in which said spacer insulates said plurality of electrodes respectively; and an insulating seal sealing the terminal portions of said housing as well as said electrodes and said spacer.
According to the pressure sensitive sensor having the above structure, the terminal portions of the housing are sealed by the seal portion. Therefore, no foreign matter such as water droplets, enters the housing from the opening portions of the terminal portions, thus preventing erroneous operation. Here, a spacer is disposed between the plurality of electrodes at the terminal portions of the housing. This, even if external pressure (i.e., pressure from the exterior of the housing) acts thereon, the electrodes do not contact one another and thus do not make electrical continuity. For this reason, even if pressure acts on the housing when the terminal portions of the housing are sealed by the seal portion, this pressure does not cause the electrodes to contact each other. This makes it easy to form a seal portion by molding with, for example, a synthetic resin material, thereby making it possible to enhance work efficiency and to reduce costs.
The pressure sensitive sensor preferably comprises a support member supporting connecting portions which connect connecting means and said plurality of electrodes, said connecting means electrically connecting said plurality of electrodes to a determination means from sides of the terminal portions of said housing, said determination means determining whether said plurality of electrodes are contacting one another so as to make electrical continuity said support member together with said plurality of electrodes and said spacer being sealed by said seal.
According to the pressure sensitive sensor having the above structure, the support member which supports the connecting means for electrically connecting the electrodes and the determination means is, together with the electrodes and the spacer, sealed by the seal portion. Accordingly, no foreign matter such as water droplets adheres to the connecting portions of the electrodes and the connecting means at the support member, thus making it possible to prevent erroneous operation. Further, sealing by the seal portion enables improvement of corrosion-resistance and maintenance of the states of the electrical and mechanical connection.
Furthermore, as stated above, if the seal portion is formed by, for example, molding with synthetic resin material, and the synthetic resin material, when molten, is provided with viscosity and stickiness, then the seal portion supports the connecting portions of the support member from the outer side. In this sense as well, it is possible to maintain the state of mechanical connection.
Preferably, the support member is integral with the spacer in the pressure sensitive sensor.
According to the pressure sensitive sensor having the above structure in which the support member is integral with the spacer, the number of parts can be decreased and costs can be reduced. In addition, if the spacer is inserted between the electrodes from the terminal portion of the housing, the support member can be naturally arranged in the vicinity of the terminal portion. In this state, the support member has been positioned, and thus, the work efficiency in the assembly process improves.
A pressure sensitive sensor terminal processing method of a second aspect according to the present invention is a method for sealing terminal portions in a pressure sensitive sensor in which at least one end of each of a plurality of electrodes is pulled out and the plurality of electrodes are fixed, so as to be spaced apart from each other with a space therebetween, in an insulating housing whose interior is hollow and which is elastically deformed by external pressure and at which the terminal portions, which are open, are provided, the pressure sensitive sensor sensing external pressure by the plurality of electrodes being made to contact each other, due to the external pressure, so as to make electrical continuity, wherein disposing an insulating spacer in the space between said plurality of electrodes to come in contact with said plurality of electrodes correspondingly to the inner terminal portions of said housing in which said spacer insulates said plurality of electrodes respectively; and sealing the terminal portions of said housing as well as said spacer by an insulating seal member.
According to this pressure sensitive sensor terminal processing method, the terminal portions of the housing are sealed by the seal portion with the insulating spacer disposed between the plurality of electrodes. Therefore, even if pressure acts at the housing when the seal portion seals the terminal portions, the spacer limits the elastic deformation of the housing at the terminal portions, thereby preventing the electrodes from contacting one another during molding. As a result, it is possible to form the seal portion by, for example, molding with synthetic resin material, and to enhance work efficiency as well as to reduce costs.
It is preferable that in the pressure sensitive sensor terminal processing method, supporting connecting portions which connect a connecting means and said plurality of electrodes by a support member, said connecting means connecting said plurality of electrodes to a determination means from sides of the terminal portions of said housing, said determination means determining whether said plurality of electrodes are contacting one another so as to make electrical continuity, and sealing said support member as well as said housing and said spacer sealing by said seal member.
According to the pressure sensitive sensor terminal processing method having the above structure, the connecting members, which are electrically connected to the determination means, are electrically connected to the electrodes at the terminal portions of the housing, and the connecting portions are supported by the support member. In addition, in this supporting state, the support member as well as the housing and electrodes are sealed by the seal member. Therefore, no foreign matter such as water droplets adhere to the connecting portions, thereby making it possible to prevent erroneous operation. In addition, since the support member itself is sealed within the seal portion, corrosion resistance of the connecting portions improves and the state of electrical and mechanical connection can be maintained.
Further, as stated above, if the seal portion is formed by, for example, molding with synthetic resin material, and the synthetic resin material, when being molten, is provided with viscosity and stickiness, then the seal portion supports the connecting portions of the support member from with outer side. In this sense as well, the mechanical connecting state can be maintained.
It is preferable that in the pressure sensitive sensor terminal processing method, said support member is integral with said spacer, and said spacer is inserted from said terminal portions into the space between said plurality of electrodes such that said support member is disposed near said terminal portions.
According to the pressure sensitive sensor terminal processing method having the above structure, the support member is integral with the spacer, and the spacer is inserted between the electrodes from the terminal end portion of the housing, thereby installing the spacer and disposing the support member in the vicinity of the terminal portion. Here, due to the fact that the spacer is integral with the support member, if the spacer is inserted between the electrodes and is supported between the electrodes, the support member is also supported by the electrodes through the spacer outside the terminal portion. In this way, the support member can be made quasi-integral with the electrodes and the housing merely by inserting the spacer. Thus, the assembly process is facilitated. In addition, there is no need to support the housing and the support member separately during the sealing operation, thus making it possible to enhance the work efficiency of the sealing operation.
A second object of the present invention is to provide a pressure sensitive sensor and a pressure sensitive sensor manufacturing method in which inadvertent short-circuiting of the electrode wires outside the housing can be prevented.
To attain the aforementioned second object, a pressure sensitive sensor of the third aspect according to the present invention comprises: an insulating hollow housing elastically deformable by external pressure, at least four elongated electrode wires disposed within said housing so as to be set apart from one another in a direction substantially orthogonal to a longitudinal direction of said housing, each electrode wire having both longitudinal end portions thereof pulled out from said housing, said electrode wires together with said housing being bent by an external pressure acting on said housing such that said electrode wires can contact one another; a resistor which is disposed at ones of longitudinal direction end portions of said electrode wires and whose both terminals are electrically connected to each of two electrode wires out of said at least four electrode wires; connecting portions for connecting a longitudinal direction another end portion of one of the two electrode wires connected to said resistor to a longitudinal direction another end portion of one of at least two electrode wires unconnected to said resistor, and for connecting a longitudinal direction another end portion of another of the two electrode wires connected to said resistor to a longitudinal direction another end portion of another of the at least two electrode wires unconnected to said resistor; and an insulating support member provided on a side of said housing so as to correspond to the longitudinal direction one end portions of said electrode wires, partitioning the electrode wires connected to said resistor from the electrode wires unconnected to said resistor, and supporting the longitudinal direction one end portions of each of said electrode wires.
According to the pressure sensitive sensor having the above structure, in a normal state (i.e., a state in which no external pressure is acting on the housing), current flows from one of at least two electrode wires to which the resistor is not connected, through the connecting portions on the longitudinal direction other end portion of this electrode wire, to one of the two electrode wires to which the resistor is connected. Moreover, this current flows through the resistor to the other one of the two electrode wires to which the resistor is connected, and then flows through the connecting portions provided on the longitudinal direction other end portion of this electrode wire, to another one of the at least two electrode wires to which the resistor is not connected.
If external pressure is applied to the housing from the outside of the housing, the housing is elastically deformed, and some of or all of the at least four electrode wires provided within the housing are bent and relatively displaced in directions of approaching each other. As a result, some of the electrode wires contact each other and a short-circuit occurs. At this time, the current flowing through the electrode wires does not flow through the resistor. Accordingly, the current value of the current flowing to the other one of the at least two electrode wires to which the resistor is not connected differs from the current value in a case where current flows through the resistor (i.e., in a normal state). By detecting the variation in the current value, it is possible to detect whether an external pressure acts on the region at which the housing is provided (i.e., the region at which the pressure sensitive sensor of the present invention is provided).
The pressure sensitive sensor of the present invention comprises an insulating support member provided at one side of the housing. The support member partitions the electrode wires connected to the resistor from those which are not connected to the resistor. The electrode wires to which the resistor is connected and those to which the resistor is not connected are supported by the support members. Therefore, even if longitudinal direction one end portions of the electrode wires and their adjacent portions in the vicinity thereof are sealed by, for example, a mold or a seal, short-circuiting does not occur between the electrode wires to which the resistor is connected and those to which the resistor is not connected, at the respective longitudinal direction one end portions and portions in the vicinity thereof during the molding or sealing process.
A pressure sensitive sensor of a fourth aspect of the present invention comprises: an insulating hollow housing elastically deformable by external pressure; at least four elongated electrode wires disposed within said housing so as to be set apart from one another in a direction substantially orthogonal to a longitudinal direction of said housing, each electrode wire having both longitudinal end portions thereof pulled out from said housing, said electrode wires together with said housing being bent by an external pressure acting on said housing such that said electrode wires can contact one another; a resistor which is disposed at ones of longitudinal direction end portions of said electrode wires and whose both terminals are electrically connected to each of two electrode wires out of said at least four electrode wires; a pair of connecting portions, one of said connecting portions connecting a longitudinal direction another end portion of one of the two electrode wires connected to said resistor to a longitudinal another end portion of one of at least two electrode wires unconnected to said resistor, the other of the connecting portions connecting a longitudinal direction another end portion of the other one of the two electrode wires connected to said resistor to a longitudinal direction another end portion of another one of the at least two electrode wires unconnected to said resistor; and a support member provided between said pair of connecting portions on a side of said housing so as to correspond to the longitudinal direction other end portions of said electrode wires and supporting each of said pair of connecting portions while partitioning said pair of connecting portions from each other.
According to the pressure sensitive sensor having the above structure, in a normal state (i.e., a state in which no external pressure is acting on the housing), current flows from one of at least two electrode wires to which the resistor is not connected, through the connecting portions on the longitudinal direction other end portion of this electrode wire, to one of the two electrode wires to which the resistor is connected. Moreover, this current flows through the resistor to the other one of the two electrode wires to which the resistor is connected and then, through the connecting portions provided on the longitudinal direction other end portion of this electrode wire to another one of the at least two electrode wires to which the resistor is not connected.
If external pressure acts on the housing from the exterior of the housing, the housing is elastically deformed, and some of or all of the at least four electrode wires provided within the housing are bent and are displaced relatively in directions of approaching one another. As a result, some of the electrode wires contact each other, and a short-circuit occurs. At this time, the current flowing through the electrode wires does not flow through the resistor. Accordingly, the current value of the current flowing to the other one of the at least two electrode wires to which the resistor is not connected differs from the current value in a case in which current flows through the resistor (i.e., in a normal state). By detecting a variation in the current value, it is possible to detect whether external pressure acts on the region at which the housing is provided (i.e., the region at which the pressure sensitive sensor of the present invention is provided).
The pressure sensitive sensor of the present invention comprises an insulating support member provided on one side of the housing. The support member partitions longitudinal direction other end portions of the electrode wires connected by one of a pair of the connecting portions from the longitudinal direction other end portions of the electrode wires connected by the other connecting portion. The longitudinal direction other end portions of the respective electrode wires are supported by the support member. Therefore, even if the longitudinal direction other end portions of the electrode wires and portions in the vicinity thereof are sealed by, for example, a mold or a seal, short-circuiting does not occur between the electrode wires connected by one of the connecting portions and those connected by the other connecting portion, at the longitudinal direction other end portions and portions in the vicinity thereof.
In the pressure sensitive sensor, it is preferable that an engagement portion, which is engageable with the housing and couples the support member to the housing when engaged with the housing, is provided at the support member.
In the pressure sensitive sensor having the above structure, the engagement portion is provided at the support member, and the support member is coupled with the housing by the engagement portion engaging the housing. As a result, the housing is substantially integral with the support member, and the relative deformation of the support member with respect to the housing is limited. Consequently, no force such as tensile force is applied to the electrode wires after the support member has been made to support the electrode wires, thereby making it possible to prevent malfunctions, such as breaking of the electrode wires, during the manufacturing process.
In the pressure sensitive sensor, it is preferable that the engagement portion has insulating property and is inserted into the housing from an end portion of the housing.
According to the pressure sensitive sensor with the above structure, the housing is coupled to the support member by inserting the engagement portion into the housing from an end portion of the housing.
Here, according to the pressure sensitive sensor of the present invention, the engagement portion is inserted into the interior of the housing from an end portion of the housing. Therefore, for example, the synthetic resin material for forming the mold or seal for sealing the support member and the end portions of the electrode wires is limited or prevented from entering into the housing. Further, even if the regions in the vicinity of the end portions of the housing are forcibly bent or curved when treating the leads connected to the electrode wires, no short-circuiting occurs in the vicinities of the end portions of the housing.
It is preferable that the sensor comprises a seal portion for sealing the support member and for sealing a region between the support member and the housing.
According to the pressure sensitive sensor with the above structure, the support member is sealed by the seal portion, and the seal portion can seal the end portions of the housing. Therefore, it is possible to protect the support member and regions in the vicinities of the end portions of the electrode wires from inadvertent external forces. Breaking of wires can be prevented, and entry into the housing of droplets or the like from the end portions of the housing can be prevented.
In the pressure sensitive sensor, the electrode wires are preferably arranged substantially helically within the interior of the housing in the longitudinal direction of the electrode wires.
According to the pressure sensitive sensor with the above structure, since the electrode wires are arranged substantially helically within the housing, it is possible to prevent short-circuiting of the electrode wires through the resistor when an external force acts on the housing. It is therefore possible to enable the sensor to more reliably detect that an external force is acting on the housing.
The fifth aspect of the present invention is a method for manufacturing a pressure sensitive sensor in which at least four electrode wires are disposed so as to be set apart from one another in a direction substantially orthogonal to a longitudinal direction of said electrode wires within a hollow insulating housing which can be deformed elastically by external pressure, said pressure sensitive sensor sensing that external pressure has been applied to said housing due to said electrode wires contacting each other so as to make electrical continuity, said method comprising the steps of: pulling out both end portions of said plurality of electrode wires from said housing; providing an insulating support member at an outer side of said housing correspondingly to at least ones of the both end portions of said plurality of electrode wires pulled out from said housing; providing a plurality of electrically conductive connecting members correspondingly to the both end portions of said plurality of electrode wires, causing said support member to support a plurality of connecting members at a side corresponding to said support member out of the plurality of connecting members while said connecting members at a side corresponding to said support member are partitioned by said support member, and connecting said plurality of electrode wires in series by said plurality of connecting members.
In the pressure sensitive sensor manufacturing method having the above structure, first, at least four electrode wires are arranged so as to be set apart from one another in directions substantially orthogonal to the longitudinal directions thereof in a state in which the both longitudinal end portions are pulled out from the housing. Next, an insulating support member is disposed so as to correspond to at least one end portions of the both end portions of the electrode wires, and a plurality of conductive connecting members are provided so as to correspond to the both end portions of the electrode wires. Among the plurality of connecting members, those at the side at which the support member is provided are supported by the support member while being partitioned by the support member. Therefore, at the side at which the support member is provided the connecting members partitioned by the support member do not contact one another and thus do not make electrical continuity. Further, both end portions of the electrode wires are electrically connected to these connecting members, and the electrode wires are connected in series. Therefore, if external pressure is applied to the housing and the housing as well as the electrode wires therein elastically deform, the electrode wires are contact each other and short-circuiting occurs. By detecting a variation in a current value which variation accompanies a variation in the resistance value in the short-circuited state, it is possible to detect that an external pressure is acting on the housing.
Here, in the pressure sensitive sensor manufacturing method of the present invention, as described above, at the side at which the support member is provided, the plurality of connecting members are supported by the support member while being partitioned by the support member. Therefore, the connecting members partitioned by the support member do not contact with one another and thus do not make electrical continuity. Accordingly, on the support member side, the electrode wires connected to different connecting members do not contact one another and do not make electrical continuity. For this reason, even if the longitudinal direction one end portions of the electrode wires and portions in the vicinity thereof are sealed by a mold, a seal or the like, the end portions of the electrode wires pulled out during the molding or sealing step, do not short-circuit, thus facilitating the molding or sealing step.
In the present invention, the support member may be disposed so as to correspond to one longitudinal direction end portions of the electrode wires or so as to correspond to both longitudinal direction end portions of the electrode wires.
The pressure sensitive sensor manufacturing method preferably comprises the steps of: displacing said plurality of connecting members at the side at which said support member is provided, in directions intersecting a direction of pulling out the end portions of said plurality of electrode wires pulled out from said housing toward the side at which said support member is provided; forming a plurality of opening portions in said support member, said opening portions having one opening end portion facing one of said plurality of connecting members in an opening direction of the one opening end portion and other opening end portions opening at a side opposite to said facing connecting member via said support member; and making one of a pair of electrodes for welding approach a connecting member out of said plurality of connecting members, from a side opposite to the connecting member, inserting another electrode for welding into one of said opening portions corresponding to the connecting member to be welded so as to make said another electrode for welding approach the connecting member to be welded, and energizing and then welding the connecting member to be welded with the connecting member to be welded held between said pair of electrodes for welding.
According to the pressure sensitive sensor manufacturing method having the above structure, the plurality of connecting members at the side at which the support member is provided are supported by the support member while being displaced in directions intersecting the direction in which the end portions are pulled at this side. Further, an opening portion is formed in the support member along the direction for partitioning the respective connecting members (i.e., along the direction from one connecting member to another connecting member partitioned by the support member). This opening portion has one opening end facing the connecting member at this opening end side in the opening direction thereof. On the other hand, as described above, one connecting member and the other connecting member are displaced in directions intersecting the direction in which the end portions of the electrode wires are pulled out. Therefore, the other opening end is displaced, with respect to the connecting member at this opening end side, in a direction intersecting the direction of pulling out the electrode wires.
One of a pair of electrodes for welding is made to approach one connecting member from a side opposite to the opening portion having the one opening and facing the connecting member. The other welding electrode is inserted into the other opening end of the opening portion and is made to approach the connecting member. While the connecting members are being held between the both welding electrodes, resistance welding is conducted. The connecting members are thereby made integral with the electrode wires connected to the connecting members.
Here, according to the pressure sensitive sensor manufacturing method of the present invention, although the support member is made of an insulating material, an opening portion is formed in the support member and the other electrode of the pair of electrodes for welding is inserted into this opening portion, whereby the connecting members are held between the pair of electrodes for welding. Therefore, the connecting members can be connected to the electrode wires by resistance welding. In addition, a method in which the support member as well as the connecting member are held between a pair of electrodes for welding while a portion of the support member is made conductive may be considered. However, in this case, the support member must be endowed with strength enough to withstand, for example, the holding force of the pair of welding electrodes. As stated above, according to the pressure sensitive sensor manufacturing method of the present invention, the connecting members are held between a pair of welding electrodes, but the support member is not held therebetween. Therefore, there is no need to endow the support member with particularly high strength. This allows more latitude in the selection of materials for the support member, and costs can be reduced. As mentioned above, the one connecting member and the other connecting members, which are partitioned by the support member, are displaced in a direction intersecting the direction in which the end portions of the electrode wires are pulled out from the housing. Therefore, the other opening end of the opening portion is located at a position which has been displaced with respect to the electrode wires and the connecting member on this opening end side. As a result, the electrode wires and connecting members on the other opening end portion side of the opening portion are not a hindrance to insertion of the welding electrodes from the other opening end of the opening portion, and the welding operation is thus facilitated.